This invention relates to devices for enabling sequential percutaneous dilation of a tissue opening to create a stoma to permit subsequent insertion of a large cannula, and enteral feeding tube, and so forth. More particularly, the present invention pertains to a sequential dilator that utilizes a series of telescoping dilators of gradually increasing size.
Although placement of small diameter cannulae is routinely done thousands of times each day in hospitals, medical clinics, and the like, placement of larger cannulae and other larger devices in blood vessels or hollow organs has been limited. More recently, techniques have been developed which enable gradual dilation of a small percutaneous opening to the required large size. Tapered dilators have been developed which are small at the tip and which increase in diameter to a desired dilation radius. Such tapered designs for large cannulae are typically too long for dilatoring hollow organs, such as a patient's stomach. Therefore, introduction of large cannulae by dilators with extreme tapered configuration has not been practical.
Further, techniques developed to overcome this problem have, in turn, created new problems. Some devices that comprises a series of telescoping tubes for stoma dilation have problems. For example, in a multiple tube dilation system, a smaller tube positioned in a larger tube may, at times, frictionally couple to the larger tube, making it difficult or impossible to separate the tubes, particularly after the dilator is positioned in a patient. In other dilator assemblies, telescoping tubes may be slid in both directions in telescoping relationship and pose the problem of smaller tube ends sliding within the bore of a larger tube, thereby making the small tube un-graspable by a health care provider for withdrawal from the assembly. That is, each smaller tube has substantially greater length than the larger tubes, and basically operates as a guide wire for the next tube mounted thereon. This pattern of decreasing the length of the tube with increasing diameter requires a health care provider to guess as to the desired positioning location of each telescoping section. Obviously, there is no guarantee that correct positioning will remain during patient use even if the correct position is initially applied. This unpredictable character not only increases risk to the patient, but also adds difficulty to the attending health care providers.
It would be desirable to have a simple and more reliable approach to patient cannulation which does not depend on the exercise of extreme care by health care providers for proper emplacement of a catheter, an enteral feeding tube, and so forth. Such a device would permit introduction of a series of telescoping tubes of increasing size, each having a short, tapered tip, and each having a radial ring or stop, which would prevent the next larger tube from extending beyond the previous tube. Further, the radial stop would provide sufficient area of the next proceeding tube so that a health care provider could readily grasp the next tube for introduction through the tissue opening.
In such a dilator assembly, an introducer or base dilator would be configured to feed over an initial guide wire placed by an introducer needle. Desirably, at an opposite end of such a base dilator, a spaced-apart series of radially grouped, axially-aligned bars would be positioned to extend from an external circumference of the base dilator. Each group of bars would desirably be of an increasing diameter; preferably, the outer diameter of the next larger tube in the telescoping sequence of tubes. The bars would be separated by a gap. The bars would desirably cooperate with each tube. That is, retaining rings on the tubes would fit into gaps on the bars, while each group of bars would contact an end of a tube which was substantially similar in diameter an outer diameter of the bars. In this manner, the series of telescoping tubes would be encouraged into the proper series of deployment, and this design would decrease the likelihood of two or more tubes frictionally engaging and becoming inseparable either during or after the creation of a patient's stoma.
Such a device also desirably includes a luer lock fitting to permit luminal access to the vessel or organ into which the stoma has been created. A peel-away sheath is desirably provided as part of such a stoma dilator. The peel away sheath, while initially attached to the dilator, would be easily detachable to permit the sheath to retain the desired dilation of the stoma while the dilator was removed. The sheath would then allow another device, such as an enteral feeding tube, to be positioned into the patient via the sheath. The sheath would then be easily detached, desirably split into at least two pieces for removal from the stoma without interference with the remaining device.